The invention relates to a light emitting device such as a light emitting diode (LED) and/or lasers with staggered quantum wells (QWs) as the active regions.
An LED is a semiconductor diode that emits incoherent narrow-spectrum light when electrically biased in the forward direction of a p-n junction. This effect is a form of electroluminescence.
An LED typically comprises a small area source, often with extra optics added to the chip that shape its radiation pattern. Color of emitted light depends on semiconductor material composition and can be infrared, visible, or near-ultraviolet. The LED can comprise a chip of semiconducting material impregnated or doped with impurities to create the p-n junction. Charge-carriers—electrons and holes—flow into the junction from electrodes with different voltages. When an electron meets a hole, it falls into a lower energy level and releases energy in the form of a photon (light) causing current flow from the p-side, or anode, to the n-side, or cathode. The wavelength of the light emitted, and hence its color, depends on the band gap energy of the materials forming the p-n junction.
An optoelectronic device is based on the quantum mechanical influences of light on semiconducting materials. An optoelectronic device can include a multilayer semiconductor structure comprising a GaN layer and an active region comprising at least one QW layer of InGaN and GaN. In a typical InGaN QW, performance (luminescence efficiency) can be adversely affected by 1) defect density (threading dislocation) and 2) the existence of an electrostatic field. A high threading dislocation density leads to low radiative efficiency. Spontaneous and piezoelectric polarization of the InGaN/GaN QW can induce a built-in electrostatic field that results in significant reduction of electron-hole wavefunction overlap Γe_hh that reduces QW radiative recombination rate and optical gain.
There is a need for an InGaN/GaN QW with reduced defect, density and electron-hole wavefunction overlap Γe_hh, for achieving higher radiative efficiency and optical gain.